The present invention is related to a coal cutter drum assembly.
FIGS. 1 and 2 are assembled and partially exploded views of a prior art coal cutter drum assembly 110 that is designed for installation on a highwall mining machine manufactured and distributed by Bucyrus International, Inc. of Milwaukee, Wis. This highwall mining machine is also known as the “Terex SHM” mining machine, as it was previously marketed and distributed by Terex Corporation and its predecessor-in-interest, Superior Highwall Miners, Inc. (“SHM”) of Beckley, West Va. In any event, as shown in the views of FIGS. 1 and 2, the coal cutter drum assembly 110 includes a cutter drum 112 that is mounted for rotation around a cutter drum shaft 114 and relative to left and right shear arms 116, 118 that extend from the mining machine. Multiple bit retainers 120 are then secured to the external surface of the cutter drum 112 in a helical pattern, with each bit retainer 120 receiving and securing a cutting bit (not shown in FIGS. 1 and 2). To effectuate rotation of the cutter drum 112, at either end of the cutter drum is a sprocket 180, 182 that is adapted to receive a chain (not shown) from a drive system of the mining machine. Thus, in operation, the cutter drum 112 is advanced into a coal seam while rotating, and the cutting bits engage and cut coal from the coal seam, as described, for example, in U.S. Pat. Nos. 5,848,825; 5,938,289; and 6,042,191, each of which is assigned to Superior Highwall Miners, Inc. (“SHM”) of Beckley, West Va. and incorporated herein by reference.
While the coal cutter drum assembly 110 shown in FIGS. 1 and 2 works for coal seams with a height of 30 inches or greater, many of the larger coal seams suitable for high wall mining have already been mined, at least those larger coal seams in the Appalachian coal mining region. Thus, many remaining coal seams have a height that is less than 30 inches. Since a coal seam has rock on the top of the seam and on the bottom of the seam, if the coal cutter drum assembly 110 described above was used to mine a smaller coal seam, the coal cutter drum assembly 110 would cut more rock than desired, contaminating the mined coal and slowing mining production since it takes longer to cut rock as compared to coal. Thus, to mine smaller coal seams without cutting and mixing adjacent rock into the mined coal and/or slowing production, it would be desirable to use a cutter drum 112 with a smaller diameter.
However, it is not possible to simply replace the cutter drum 112 of the coal cutter drum assembly 110 with a cutter drum having a smaller outer diameter. Specifically, highwall coal mining requires high-powered motors to rotate the cutter drum 112, and thus, large-diameter bearings are required to support the cutter drum 112 as it is driven by the motors. For example, as shown in FIG. 2, in one prior art construction, roller bearings 170, 172 are positioned on either end of the cutter drum 112. In this example, the outer rings or races for each bearing 170, 172 are fit inside of the cutter drum 112, i.e., within the tube that forms the body of the cutter drum 112. The inner rings carrying the rollers are then mounted to the cutter drum shaft 114.
Because of such positioning of the bearings 170, 172, the size of the cutter drum 112 is limited by the size of the bearings that are required to support the cutter drum 112 as it is driven. For example, if the required bearings have a 10-inch outside diameter, the tube that forms the body of the cutter drum 112 would have to have an outer diameter of approximately 13 inches—with a 10-inch inner diameter for the bearings and a 1.5-inch wall thickness. Then, once the bit retainers 120 are secured to the external surface of the cutter drum 112, the cutting bits would extend approximately 7 inches on each side of the cutter drum 112, which is necessary to allow the mined coal to flow over the cutter drum 112 to the cutter conveying augers (not shown) and clear the mined coal from the cutter drum area. In other words, once the bit retainers 120 and associated cutting bits are secured to the external surface of the cutter drum 112, the total cutter drum diameter would be at least 27 inches. It would be virtually impossible to cleanly mine a coal seam with a height that is less than 30 inches using such a cutter drum assembly.
Finally, although not critical to an understanding of the present invention, to complete the description of FIG. 2, it should be noted that there is a first pair of face seals 174 positioned at one end of the cutter drum 112 and a second pair of face seals 176 positioned at an opposite end of the cutter drum 112. One of the rubber O-rings with one half of the first pair of face seals 174 is fit into the shear arm 116, while the other half of the first pair of face seals 174 is fit into the sprocket 180. Similarly, one end of the rubber O-rings with one half of the second pair of face seals 176 is fit into the shear arm 118, while the other half of the second pair of face seals 176 is fit into the sprocket 182. Thus, once assembled, these pairs of face seals 174, 176 prevent leakage of oil from the cutter drum 112.